/// <summary>
/// When overriden in a derived class, generates a crossover based on the parent entities.
/// </summary>
/// <param name="parents">The <see cref="GeneticEntity"/> objects to be operated upon.</param>
/// <returns>
/// Collection of the <see cref="GeneticEntity"/> objects resulting from the crossover.
/// </returns>
protected override IEnumerable <GeneticEntity> GenerateCrossover(IList <GeneticEntity> parents)
{
if (parents == null)
{
throw new ArgumentNullException(nameof(parents));
}
TreeEntityBase tree1 = (TreeEntityBase)parents[0];
TreeEntityBase tree2 = (TreeEntityBase)parents[1];
int crossoverLocation1 = RandomNumberService.Instance.GetRandomValue(tree1.GetSize());
int crossoverLocation2 = RandomNumberService.Instance.GetRandomValue(tree2.GetSize());
TreeNode swapNode1 = GetSwapNode(tree1, crossoverLocation1);
TreeNode swapNode2 = GetSwapNode(tree2, crossoverLocation2);
TreeHelper.Swap(swapNode1, swapNode2);
List <GeneticEntity> geneticEntities = new List <GeneticEntity>
{
tree1,
tree2
};
return(geneticEntities);
}
/// <summary>
/// Returns the node at the specified prefix position.
/// </summary>
private static TreeNode GetSwapNode(TreeEntityBase tree, int nodePosition)
{
Debug.Assert(nodePosition < tree.GetSize(), "nodePosition must be less than the size of the tree.");
return(tree.GetPrefixTree().Where((node, index) => index == nodePosition).FirstOrDefault());
}